docs(linter/typescript/switch-exhaustiveness-check): clarify default case comment pattern (#26100)

## Summary
- clarify that `defaultCaseCommentPattern` recognizes a trailing comment in place of an omitted `default` clause
- document the required location, absence of a live `default`, and the `considerDefaultExhaustiveForUnions` requirement for union switches
- regenerate the JSON schema and TypeScript configuration types

Fixes #26087